﻿/*
 * NullableDictionary - A simple Dictionary that can handle null as a key
 *
 * Author: Phillip Piper
 * Date: 31-March-2011 5:53 pm
 *
 * Change log:
 * 2011-03-31  JPP  - Split into its own file
 * 
 * Copyright (C) 2011-2014 Phillip Piper
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * If you wish to use this code in a closed source application, please contact phillip.piper@gmail.com.
 */

using System;
using System.Collections.Generic;
using System.Text;
using System.Collections;

namespace Fluent {
	/// <summary>
	/// A simple-minded implementation of a Dictionary that can handle null as a key.
	/// </summary>
	/// <typeparam name="TKey">The type of the dictionary key</typeparam>
	/// <typeparam name="TValue">The type of the values to be stored</typeparam>
	/// <remarks>This is not a full implementation and is only meant to handle
	/// collecting groups by their keys, since groups can have null as a key value.</remarks>
	internal class NullableDictionary<TKey, TValue> : Dictionary<TKey, TValue> {
		private bool hasNullKey;
		private TValue nullValue;

		public new TValue this[TKey key] {
			get {
				if (key != null) {
					return base[key];
				}

				if (hasNullKey) {
					return nullValue;
				}

				throw new KeyNotFoundException();
			}
			set {
				if (key == null) {
					hasNullKey = true;
					nullValue = value;
				}
				else {
					base[key] = value;
				}
			}
		}

		public new bool ContainsKey(TKey key) {
			return key == null ? hasNullKey : base.ContainsKey(key);
		}

		public new IList Keys {
			get {
				var list = new ArrayList(base.Keys);
				if (hasNullKey) {
					list.Add(null);
				}

				return list;
			}
		}

		public new IList<TValue> Values {
			get {
				var list = new List<TValue>(base.Values);
				if (hasNullKey) {
					list.Add(nullValue);
				}

				return list;
			}
		}
	}
}